This application claims priority of Taiwanese Application No. 091203167, filed on Mar. 15, 2002.
1. Field of the Invention
The present invention relates to a bicycle wheel rim, more particularly to a bicycle wheel rim with a reinforced base wall.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional bicycle wheel rim 1 is shown to include annular left and right tire retaining walls 11 and an annular spoke mounting wall 12 interconnecting radial inner edges of the tire retaining walls 11. The spoke mounting wall 12 is formed with a plurality of spoke fastening holes 121 that are arranged generally along a central portion of the spoke mounting wall 12 for mounting spoke fasteners 102 thereon. A plurality of spokes 101 are fastened to the spoke fasteners 102 for mounting the bicycle wheel rim 1 on two opposite ends of a hub (not shown). The aforementioned conventional bicycle wheel rim 1, however, suffers from the following drawback: Since the spoke fastening holes 121 are arranged along the central portion of the spoke mounting wall 12, the central portion of the spoke mounting wall 12 is susceptible to deformation due to the tension forces applied by the spokes 101 when the bicycle wheel rim 1 is in use.
To reinforce the strength of the bicycle wheel rim, it has been proposed in the art to provide a bicycle wheel rim 2 with a two-layer base wall unit which includes an annular spoke mounting wall 22 extending between the tire retaining walls 21, and an annular bridging wall 23 disposed around the spoke mounting wall 22 and bridging the tire retaining walls 21, as shown in FIG. 3. The base wall unit further includes a pair of inclined reinforcing walls 24 extending between the bridging wall 23 and the spoke mounting wall 22. To permit the installation of spoke fasteners 203, the bridging wall 23 must be formed with a plurality of through holes 231 aligned respectively with spoke fastening holes 221 in the spoke mounting wall 22 to permit passage of the spoke fasteners 203 therethrough. The through holes 231 and the spoke fastening holes 221 are typically formed by punching. However, since the through holes 231 and the spoke fastening holes 221 differ in size, formation of the through holes 231 and the spoke fastening holes 221 thus involves a complicated punching process. Moreover, chips of the metal of the wheel rim 2 removed during the punching process could be received within the cavity 223 that is confined by the spoke mounting wall 22, the bridging wall 23, and the reinforcing walls 24, and are difficult to be discharged therefrom.
Therefore, the main object of the present invention is to provide a bicycle wheel rim that has a reinforced base wall and that permits formation of spoke fastening holes in the base wall through a simple punching process.
According to a first aspect of the present invention, a bicycle wheel rim includes an annular rim body with a central axis. The rim body includes annular left and right tire retaining walls which are spaced-apart from each other, and an annular connecting wall. Each of the tire retaining walls has a radial inner edge proximate to the central axis of the rim body. The base wall interconnects the radial inner edges of the left and right tire retaining walls, and cooperates with the tire retaining walls to confine a tire retaining space thereamong. The base wall includes left and right corner parts disposed adjacent and connected to the left and right tire retaining walls, respectively, and an intermediate part extending between the corner parts. The intermediate part has a vaulted portion, which is vaulted in a radial inward direction with respect to the central axis. The intermediate part is formed with a first set of spoke mounting holes which are distributed along the base wall between the vaulted portion and the left corner part, and a second set of spoke mounting holes which are distributed along the base wall between the vaulted portion and the right corner part.
According to a second aspect of the present invention, a bicycle wheel rim includes an annular rim body with a central axis. The rim body includes annular left and right tire retaining walls which are spaced-apart from each other, and an annular base wall. Each of the tire retaining walls has a radial inner edge proximate to the central axis of the rim body. The base wall interconnects the radial inner edges of the tire retaining walls, and cooperates with the tire retaining walls to confine a tire retaining space thereamong. The base wall includes left and right corner parts disposed adjacent and connected to the left and right tire retaining walls, respectively, and an intermediate part extending between the corner parts. The intermediate part has a vaulted portion which is vaulted in a radial outward direction with respect to the central axis, a left wall section extending between the vaulted portion and the left corner part and formed with a first set of spoke mounting holes, and a right wall section extending between the vaulted portion and the right corner part and formed with a second set of spoke mounting holes. Each of the left and right wall sections has a first terminating edge connected to the respective one of the left and right corner parts, and a second terminating edge opposite to the first terminating edge and connected to the vaulted portion. The intermediate part of the base wall further includes a bridging wall, which extends between the second terminating edges of the left and right wall sections. The bridging wall is flush with the left and right wall sections.